首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   410篇
  免费   50篇
  2021年   7篇
  2020年   4篇
  2019年   4篇
  2018年   7篇
  2017年   5篇
  2016年   3篇
  2015年   12篇
  2014年   13篇
  2013年   12篇
  2012年   16篇
  2011年   24篇
  2010年   18篇
  2009年   11篇
  2008年   28篇
  2007年   25篇
  2006年   22篇
  2005年   13篇
  2004年   9篇
  2003年   10篇
  2002年   16篇
  2001年   21篇
  2000年   18篇
  1999年   12篇
  1998年   7篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1993年   5篇
  1992年   17篇
  1991年   8篇
  1990年   13篇
  1989年   10篇
  1988年   8篇
  1987年   5篇
  1986年   2篇
  1985年   3篇
  1984年   8篇
  1983年   6篇
  1981年   2篇
  1980年   3篇
  1978年   2篇
  1976年   4篇
  1975年   2篇
  1974年   3篇
  1973年   2篇
  1971年   2篇
  1969年   3篇
  1968年   5篇
  1966年   5篇
  1959年   2篇
排序方式: 共有460条查询结果,搜索用时 441 毫秒
1.
Summary The junctional complexes of cells in the outer arachnoid layer overlying the cerebral cortex of 2-week-old rats were examined with freeze-fracture electron microscopy up to 60 min after transcranial cold injury to the dorsal surface of the brain. Within 30 min after injury, areas of gap and tight junctions with morphological features characteristic of junction formation and/or junction disruption were found scattered among normal junctional complexes in some arachnoid cells. Within 60 min after injury, tight junctions with features typical of less leaky zonulae occludentes were present in all arachnoid cells examined. These morphological features include increases in the number of tight junctional strands and the number of strand-to-strand anatomoses. Gap junctions were interspersed among the tight junctional strands, and many were completely encircled by the strands. The increase in the number and complexity of the tight junctional strands in response to brain injury may be the morphological basis for the maintenance of the cerebrospinal fluid-blood dural barrier.This study was supported by the National Institute of Neurological and Communicative Disorders and Stroke Grant NS20590. The opinions or assertions contained herein are the private ones of the authors and are not to be construed as official or reflecting the views of the DoD or the USUHS. The experiments reported herein were conducted according to the principles set forth in the Guide for Care and Use of Laboratory Animals, Institute of Laboratory Animal Resources, National Research Council, DHEW Pub. No. (NIH) 78-23  相似文献   
2.
M Gulotta  D J Goss  M Diem 《Biopolymers》1989,28(12):2047-2058
The first observation of ir vibrational CD (VCD) in small model DNA molecules is reported. The VCD signals in the 1550-1750-cm-1 spectral region, which originate from coupling of carbonyl stretching modes of the nucleic acid bases, are found to be sensitive to the handedness of the polymer helix. The formalism to calculate VCD intensities of polymers is developed from the exciton model derived earlier by Tinoco [(1963) Radiation Res. 20, 133; (1960) J. Chem. Phys. 33, 1332; (1964) J. Am. Chem. Soc. 86, 297] and Schellman and co-workers [(1975) Biopolymers 14, 173; (1969) J. Phys. Chem. 73, 28]. The resulting equations, which are a direct extension of the dimeric case known as the "coupled oscillator," are used in model calculations of the helical polymers.  相似文献   
3.
4.
5.
In order to understand the possible role of eucaryotic initiator factor 3 (eIF-3) in maintaining a pool of eucaryotic subunits, we have measured the effects of eIF-3 on the equilibria and kinetics of ribosomal subunit association and dissociation. The ribosomal subunit interactions have been studied by laser light scattering, which does not perturb the system. We find that eIF-3 reduces the apparent association rate of reticulocyte, wheat germ, and Artemia ribosomes. The kinetics of the reassociation for a shift in [Mg2+] from 0.5 to 6 mM are best explained by a model where eIF-3 dissociates from the 40S subunits prior to association of the 40S and 60S subunits. Static titrations indicate there is some binding of eIF-3 to 80S ribosomes at lower [Mg2+].  相似文献   
6.
When discs of frontal periosteum from presumptive antler sites of 6-8 month old male fawns of the fallow deer are grafted beneath the foreleg skin, they will differentiate into pedicle bones and induce small antlers in the overlying integument. These antlers shed their velvet in the fall, and in succeeding years are replaced by larger outgrowths not exceeding 7 cm in length. Periosteal transplants 1.5 cm in diameter gave rise to ectopic antlers in 100% of the grafts, while discs measuring 1.05 cm, 0.75 cm and 0.4 cm did so in only 20% of the cases. Conversely, the donor sites produced antlers in 20-23% of the cases following removal of 1.05 cm or 1.5 cm of periosteum, while 80% and 100% grew antlers after deletions of 0.75 cm and 0.4 cm discs of periosteum, respectively. Semicircular grafts of periosteum induced antler development in most cases, especially when derived from the lateral halves of the antlerogenic region on the frontal bone. These findings confirm that the histogenesis of a deer's first pedicle and antler resides in the frontal periosteum over an area about 1.5 cm wide. They also show that leg skin is capable of antlerogenic development under the inductive influence of frontal periosteum, and that integumental wounding may enhance inductive interactions.  相似文献   
7.
L J Parkhurst  D J Goss 《Biochemistry》1984,23(10):2180-2186
Oxygen and CO ligand binding kinetics have been studied for the hybrid hemoglobin (Hb) alpha (human):beta (carp), hybrid II. Valency and half-saturated hybrids were used to aid in the assignment of the conformations of both chains. In hybrid II, an intermediate S state occurs, in which one chain has R- and the other T-state properties. In HbCO at pH 6 (plus 1 mM inositol hexaphosphate), the human alpha-chain is R state and the carp beta-chain is T state. We have no evidence at this pH that the carp beta-chain ever assumes the R conformation. At pH 6, the human alpha-chain shows human Hb R-state kinetics at low fractional photolysis and T-state rates for CO ligation by stopped flow. At pH 7, the human-chain R-state rate slows toward a carp hemoglobin rate. The carp beta-chains, on the other hand, react 50% more rapidly in the liganded conformation than in carp hemoglobin, and while the human alpha-chains are in the R state, the two beta-chains appear to function as a cooperative dimer. In this hemoglobin, the chains appear to be somewhat decoupled near pH 7, allowing a sequential conformational change from the R state in which the beta-chains first assume T-state properties, followed by the alpha-chains. The rate of the R-T conformational change for the carp beta-chains is at least 300 times greater than that for the human alpha-chains. At pH 9, the R----T conformational transition rate is at least 200 times slower than that for human hemoglobin.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
8.
9.
The gene for the androgen receptor, mutations at which cause the X-linked androgen insensitivity syndrome, has been localized to the q11----q12 region of the human X chromosome by analysis, using a cloned cDNA for the androgen receptor, of somatic cell hybrid panels segregating portions of the X chromosome. A moderate-frequency HindIII RFLP has been found which should be useful in genetic linkage analysis of the various inherited forms of androgen insensitivity.  相似文献   
10.
T Xiang  D J Goss    M Diem 《Biophysical journal》1993,65(3):1255-1261
We report observed and computed infrared (vibrational) circular dichroism spectra of a number of polyribonucleic acids in aqueous solutions in the 1600-1750 cm-1 spectral region, in which C = O and some nucleotide base ring stretching vibrations occur. The experimental data are compared with results calculated using different levels of sophistication within the exciton approach. We find that observed band shapes are generally well reproduced by these models, particularly if care is taken to determine the direction of the vibrational dipole transition moments accurately.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号